This invention is an improved continuous furnace and method of operation and is particularly applicable to continuous gasification of waste material. The furnace of the present invention has an improved feed means, discharge means, means to introduce steam and air and an improved method of operation.
Feed systems of furnaces, and particularly continuous furnaces, do not have the ability to continuously compact feed materials such as waste. Presently, when waste material must be compacted before being charged into a furnace, a compacting ram is used. It is difficult to use a compacting ram in a continuous feed stream to a furnace. Complicated sealing means must be provided when a compacting ram is placed in the feed path of a furnace where it is desired to keep a seal between it and the furnace.
The use of steam in furnaces is well known. Steam is used for two purposes; the first is as a means for cooling and the second is as a means to promote more efficient combustion of the fuel or charge to be burned. When steam, air and carbon are present in the furnace mix at elevated temperatures, an endothermic reaction proceeds resulting in highly combustible reaction products including hydrogen and carbon monoxide which burn in the presence of oxygen creating intense heat which in turn promotes more efficient burning of the fuel or charge to be burned.
Furnaces are known which take advantage of the endothermic reaction of the steam feed as a means to cool or the exothermic reaction of the burning of the highly combustible reaction products as a means for more efficient combustion, or both the steam feed cooling and the exothermic reaction. Both effects have been used in furnaces by using separate steam inputs at different places within furnaces to accomplish specific purposes.
Furnaces using steam have had combustion of fuel or other material as their sole purpose while the present invention concerns gasification of waste material. Where steam and air have been used in furnaces, a continuing concern has been the methods of injecting or feeding both the steam and the air into the furnaces. This concern is evidence of the desire to control either the endothermic reaction of the steam or the exothermic reaction of the steam in the furnace and to obtain a uniform air and steam mixture.
In continuous sealed furnaces, mechanical devices such as double tipping valves are used to sealingly discharge ash from the furnace. Such devices usually have double seals to allow a seal to be maintained during the discharge. Another mechanical device is a cone which eccentrically rotates above the discharge port of the furnace. The cone supports the charge bed and agitates it as it rotates with the ash falling into a sealed ash hopper from between the cone and the furnace wall. It would be desireable to eliminate moving mechanical ash discharge devices from the body of the furnace and from immediate area of the discharge port so as to allow repair and replacement without significantly affecting furnace operation.